Cropping is the process of selecting an area of an image and discarding the remainder of the image. Cropping allows the subjects of photographs such as people to be emphasized in the photographs. Cropping also allows the aspect ratio of images to be changed. The process of cropping an image involves balancing the increase in emphasis with the information lost in the discarded region of the image. Manually cropping digital images can be a time consuming process, therefore computer implemented automatic cropping methods have been developed. For example, U.S. Pat. No. 6,654,506 discloses a; method and computer program for cropping a digital image which involves inputting a belief map of a photographic image, selecting a zoom factor and a crop window, clustering regions of the belief map to identify background portions, secondary portions and main portions, positioning a crop window such that the crop window is centered around a main portion having a highest belief value, moving the crop window such that the crop window is included completely within the image, moving the crop window such that the sum of belief values is at a maximum and cropping the image according to the crop window. The belief value at a location in the belief map indicates the importance of a photographic subject at the same location in the photographic image.
US2002/019861 discloses an apparatus and a method of using an electronic camera to capture and crop electronic images. An electronic imaging device processes the electronic image to identify one or more features relevant to the composition of the electronics image, each such feature having one or more compositionally significant properties from amongst a plurality of different predetermined compositional properties, and each such feature occupying a sub-region of the electronic image. Then the device selects one or more compositional rules from a set of predetermined compositional rules, based on the relevance of the compositional rules to the compositionally significant properties of one or more of the identified features. Then the device determines one or more suitable crop boundaries for applying one or more of the selected compositional rules.